1. Field of the Invention
The present invention relates to a freewheel clutch which is shiftable in two rotational directions. The invention also relates to a method of transmitting power using a freewheel clutch which is shiftable in two rotational directions.
2. Background of the Invention
Freewheel clutches or freewheels are in particular known in bicycle engineering. Austrian application AT-194253, for instance, discloses a freewheel and gear hub having a back-pedal brake for bicycles wherein ratchets operate without any noise. These ratchets are controlled by a friction sleeve which frictionally slides in the sleeve or in an annular member which is fixedly connected to the hub sleeve. The friction sleeve includes recesses for the ratchets, noses for limiting the rotation, and frictional slide springs which rest on the annular member.
Furthermore, U.S. Pat. No. 2,181,665 shows a simple construction of a freewheel acting in one direction. In this design, a spring-biased ratchet engages into recesses which are provided for the ratchet upon rotation of the hub in one rotational direction. However, it does not engage into the recesses upon rotation in the other rotational direction.
Furthermore, German application DE-3326420 shows a freewheel clutch which utilizes a driving clutch, half which includes two axially offset eccentrics. However, the freewheel clutch is only intended for transmitting a rotational movement from a drive element to a driven element in one direction of rotation. Moreover, an independent free rotational movement of the driven element is ensured in the same direction of rotation when the speed thereof exceeds that of the drive element.
Despite the great number of solutions offered in the field of bicycles or similar devices, there continues to exist a need for a freewheel clutch which can be utilized, in particular, in pedal vehicles for children such as tricycles or Kettcars(copyright) which allow pedaling in both the forward direction and the rearward direction from an initial inoperative position. Such a design should easily permit both a forward movement and a rearward movement, respectively, of the vehicle. Furthermore, there is also a need for a freewheeling design which acts in both directions and prevents the pedals from rotating, for instance, during travel in sloping terrain or while the vehicle is being pushed. Moreover, since a pedal drive acts in both directions, the freewheel must also be operative in both directions for reasons of safety. Accordingly, such a design may make these devices safer by preventing a user from injuring their legs or feet on the pedals.
The present invention provides for a freewheel clutch of simple construction and relatively low manufacturing costs which is shiftable in both rotational directions and includes a freewheel condition which acts in both rotational directions.
According to the invention there is provided a freewheel clutch which is shiftable in both rotational directions, e.g., forwards or backwards, clockwise or counterclockwise, etc., and which includes a double-acting freewheel. The clutch includes a driver or catch which is fixedly and/or securely connected to a drive shaft and further includes an engagement mechanism which is arranged between the drive shaft and a driven shaft.
Additionally, the freewheel clutch utilizes a holding element which engages the engagement mechanism and which is frictionally engaged with or frictionally coupled to a fixed member which may be a vehicle frame. A spring element is utilized in the clutch such that in the inoperative state of the drive shaft, the engagement mechanism is maintained out of engagement with the driven shaft. However, in the driven state of the drive shaft, the engagement mechanism is placed into engagement with the driven shaft via the catch.
Prior to engagement of the engagement mechanism with the driven shaft, the engagement mechanism is engaged by the holding element in a non-rotating or stationary state, while the drive shaft and the catch are rotating due to pedaling. A frictional force, which is maintained between the holding element and the fixed member, is designed to be greater than a resilient force which is exerted by the spring element. This design permits the engagement of the engagement mechanism with the driven shaft when the drive shaft is rotated a predetermined amount. Furthermore, the clutch utilizes an engagement force which is created between the engagement mechanism and the driven shaft, which is greater than the frictional force between holding element and fixed member. Accordingly, as a result of this design, a power transmission from the drive shaft to the driven shaft via the catch and the engagement mechanism is thereby made possible.
Thus, according to the invention, it is possible to drive the drive shaft forwards or rearwards (i.e., clockwise or counterclockwise) by pedaling a pedal vehicle. Moreover, this design easily achieves a forwardly directed movement or a rearwardly directed movement of the vehicle, depending on the respective drive direction of the drive shaft and/or pedals. Thus the freewheel clutch according to the invention can be shifted into both rotational directions based upon movement of the pedals in the corresponding directions.
Furthermore, the invention provides a double-acting freewheel which makes it possible to move the pedal vehicle forwards or rearwards without pedaling. Accordingly, this design allows the pedals to remain stationary (e.g., not caused to be rotated) when the vehicle is pushed in either direction. Thus, when the vehicle is pushed in a forward direction, this movement will not cause forward corresponding movement of the pedals in the forward direction and vise versa. It is thus in particular possible to push pedal vehicles with children thereon forwards or rearwards without producing any rotation of the pedals. As a result, the risk of injury to the child""s feet or legs is thereby reduced.
Preferably, the engagement mechanism which is located between the drive shaft and the driven shaft is designed such that it permits a positive lock or positive engagement between a driving part and a driven part. This positive engagement design ensures a reliable connection between the driving and the driven part. However, the invention also contemplates the use of frictional engagement by the engagement mechanism between the driving part and the driven part. Such a design allows for an even simpler construction of the freewheel clutch. Of course, in each of these embodiments, the frictional force between the engagement mechanism and the driven shaft must be greater than the frictional force between the holding element and the fixed member.
Preferably, the driven shaft is designed as an internally splined hollow shaft. This allows for a compact freewheel clutch which is saves space, in particular, in the axial direction.
In order to provide for a simple construction of the freewheel clutch, the spring element is preferably designed as a spring washer or ring. The ring or washer may have an entirely annular shape or may be designed as a split ring or split washer so as to permit easy mounting and/or assembly/disassembly.
Advantageously, the engagement mechanism may be designed as a locking spline having external teeth or toothing. This design permits a reliable positive teeth to teeth engagement so as to connect or couple the drive shaft to the driven shaft.
In order to obtain a redundant engagement between the drive shaft and the driven shaft, the engagement mechanism may include two locks or engagement elements in which each engagement element utilizes an external spline, teeth or toothing.
Additionally, it is preferred that the catch is designed as a semi-annular element having two lateral wing sections. Utilizing this design, the semi-annular element part of the catch can easily be connected to the drive shaft, e.g. by conventional attachment techniques such as welding, bonding, fasteners, etc., or any combination thereof.
Moreover, in order to help reduce the risk of injury, a certain amount of motional or rotational play should exist in the drive shaft prior to the drive shaft being placed into engagement with the driven shaft. The amount of play can of course be varied for the particular purpose. However, it is preferred that this play be a total of approximately 30xc2x0. Accordingly, this design allows the pedals also have a motional or rotational play of approximately xc2x115xc2x0 in either direction and around an axis running through the drive shaft. Again, this allows for a total motional or rotational play of the pedals of approximately 30xc2x0. Stated another way, starting from a central or initial position, the pedals can be moved or rotated forwards by approximately 15xc2x0 and rearwards by approximately 15xc2x0 without the drive shaft causing corresponding movement or rotation of the driven shaft.
In order to limit the movement of the catch in axial direction, at least one of the engagement elements of the engagement mechanism advantageously includes inwardly projecting noses. Preferably, the holding element which cooperates with the engagement mechanism is designed as an annular or ring-like fork which has at least one engagement or projection arm. Moreover, a fiber friction disk or friction washer is arranged as a friction-producing element between the annular fork and the fixed member. This design permits a particularly axially compact construction. Moreover, the fiber friction washer is designed such that it can easily be replaced in case of wear.
The invention therefore provides for a freewheel clutch which is shiftable in two rotational directions, the clutch including a drive shaft which can rotate in each of two directions, a catch element which is fixedly secured to the drive shaft, a driven shaft, an engagement mechanism arranged between the drive shaft and the driven shaft, a fixed member, a holding element frictionally engaging the fixed member, and a spring element biased to release the engagement mechanism from engagement with the driven shaft. The clutch may be a double-acting freewheel clutch. The force of engagement between the engagement mechanism and the driven shaft may be greater than a frictional force produced by the frictional engagement between the fixed member and the holding element. The frictional force produced by the frictional engagement between the fixed member and the holding element may be greater than a resilient force which prevents the engagement mechanism from engaging the driven shaft. The spring element may bias the engagement mechanism towards an axis of the drive shaft. The engagement mechanism may comprise at least two engagement elements. The spring element may bias the at least two engagement elements towards an axis of the drive shaft. The engagement mechanism may comprise a friction engaging surface for frictionally engaging the driven shaft. The friction engaging surface may comprise at least one tooth. The friction engaging surface may comprise a plurality of teeth. The driven shaft may comprise a friction engaging surface having at least one tooth. The at least one tooth of the driven shaft may be adapted to engage the at least one tooth of the engagement mechanism. Rotation of the drive shaft may cause corresponding rotation of the driven shaft when the at least one tooth of the engagement mechanism engages the at least one tooth of the driven shaft.
The driven shaft may comprise a hollow shaft having a plurality of an internal spline and a plurality of internal teeth. The spring element may comprise one of a spring washer and spring ring. The spring element may comprise one of a split spring washer and split spring ring. The engagement mechanism may comprise one of an external spline and a plurality of external teeth for engaging the driven shaft. The engagement mechanism may comprise at least two engagement elements, each of the at least two engagement elements having one of an external spline and a plurality of external teeth for engaging the driven shaft. The catch element may comprise a semi-annular section having two lateral wing sections projecting therefrom. The semi-annular section may be fixedly secured to an exterior surface of the drive shaft. The semi-annular section may be fixedly secured to an exterior surface of the drive shaft by one of welding and boding.
The drive shaft may be adapted to rotate approximately 15xc2x0 in a clockwise direction before the engagement mechanism engages the driven shaft. The drive shaft may be adapted to rotate approximately 15xc2x0 in a counterclockwise direction before the engagement mechanism engages the driven shaft. The drive shaft may be adapted to rotate approximately 15xc2x0 in each of a clockwise and a counterclockwise direction before the engagement mechanism engages the driven shaft. The engagement mechanism may comprise at least one engagement element, the at least one engagement element including at least one projecting portion. The at least one projecting portion may comprise a stop for preventing the catch element from moving in the axial direction. The at least one projecting portion may comprise at least two projecting portions. The fixed member may comprises a sleeve. The sleeve may comprise an annular shoulder which frictionally engages the holding element. The sleeve may comprise an opening for receiving the drive shaft.
The holding element may comprise an annular fork. The annular fork may comprises a washer portion and at least one arm projecting from the washer section. The at least one arm may be adapted to engage at least one slot in the engagement mechanism. The at least one arm may comprise at least two arms, each of the at least two arms being adapted to engage a corresponding slot in the engagement mechanism.
The clutch may further comprise a friction washer arranged between the holding element and the fixed member. The friction washer may be arranged between the holding element and an annular shoulder of the fixed member. The friction washer may comprise one of a fiber washer and a fiber lined washer. The clutch may further comprise one of a spring washer and a corrugated washer arranged against the holding member. The clutch may further comprise a cover for enclosing the engagement mechanism. The clutch may further comprise a securing disk for securing the cover to the fixed member. Rotation of the drive shaft in at least one direction may cause the engagement mechanism to engage the driven shaft. The clutch may comprise a pedal vehicle clutch.
The invention also provides for a freewheel clutch which is shiftable in two rotational directions, the clutch including a first shaft which can rotate in each of two directions, a second shaft comprising a hollow space, an opening for receiving the first shaft, and an internal friction surface, an engagement mechanism arranged within the hollow shape, the engagement mechanism comprising an exterior friction surface, a catch element fixedly secured to the drive shaft, a fixed member comprising an opening for receiving the first shaft and an annular shoulder, a holding element for frictionally engaging the annular shoulder of the fixed member, and a spring element for biasing the engagement mechanism towards the first shaft so as to prevent the external friction surface of the engagement mechanism from engaging the internal friction surface of the second shaft, wherein rotation of the first shaft in at least one direction causes a corresponding rotation of the second shaft.
The clutch may be a double-acting freewheel clutch. The force of engagement between the engagement mechanism and the second shaft may be greater than a frictional force produced by the frictional engagement between the fixed member and the holding element. The frictional force produced by the frictional engagement between the fixed member and the holding element may be greater than a resilient force which prevents the engagement mechanism from engaging the second shaft. The engagement mechanism may comprise at least two engagement elements. The external friction surface may comprise at least one tooth. The at least one tooth may comprise a plurality of teeth. The internal friction surface may comprise one of an internal spline and a plurality of teeth. The at least one tooth of the engagement mechanism may be adapted to engage one of the internal spline and the plurality of teeth. Rotation of the first shaft may cause corresponding rotation of the second shaft when the at least one tooth of the engagement mechanism engages one of the internal spline and the plurality of teeth of the second shaft.
The spring element may comprise one of a split spring washer and a split spring ring. The engagement mechanism may comprise at least two engagement elements, each of the at least two engagement elements comprising the external friction surface, the external friction surface further comprising one of an external spline and a plurality of external teeth for engaging a corresponding spline or teeth disposed on the internal friction surface of the second shaft. The catch element may comprise a semi-annular section having two lateral wing sections projecting therefrom. The semi-annular section may be fixedly secured to an exterior surface of the first shaft by one of welding and boding. The first shaft may be adapted to rotate approximately 15xc2x0 in a clockwise direction before the engagement mechanism engages the second shaft. The first shaft may be adapted to rotate approximately 15xc2x0 in a counterclockwise direction before the engagement mechanism engages the second shaft. The first shaft may be adapted to rotate approximately 15xc2x0 in each of a clockwise and a counterclockwise direction before the engagement mechanism engages the second shaft. The engagement mechanism may comprise at least one engagement element, the at least one engagement element including at least one projecting portion. The at least one projecting portion may comprise at least two projecting portions.
The holding element may comprise an annular fork, the annular fork comprising a washer portion and at least one arm projecting from the washer section. The at least one arm may be adapted to engage at least one slot in the engagement mechanism. The at least one arm may comprise at least two arms, each of the at least two arms being adapted to engage a corresponding slot in the engagement mechanism.
The clutch may further comprise a friction washer arranged between the holding element and the annular shoulder of the fixed member. The friction washer may comprise one of a fiber washer and a fiber lined washer. The clutch may further comprise one of a spring washer and a corrugated washer arranged against the holding member. The clutch may further comprise a cover for enclosing the engagement mechanism. The clutch may further comprise a securing disk for securing the cover to the fixed member. The clutch may further comprise a friction washer arranged between the holding element and the annular shoulder of the fixed member, the friction washer comprises one of a fiber washer and a fiber lined washer, one of a spring washer and a corrugated washer arranged against the holding member, a cover for enclosing the engagement mechanism, and a securing disk for securing the cover to the fixed member, wherein the holding element comprises an annular fork, the annular fork comprising a washer portion and at least two arms, each of the at least two arms being adapted to engage a corresponding slot in the engagement mechanism. The clutch may comprises a pedal vehicle clutch.
The invention also provides for a method of transmitting power from a drive shaft to a driver shaft utilizing a freewheel clutch which is shiftable in two rotational directions wherein the drive shaft is rotatable in each of two directions, the clutch including a catch element which is fixedly secured to the drive shaft, an engagement mechanism arranged between the drive shaft and the driven shaft, a fixed member, a holding element frictionally engaging the fixed member, and a spring element biased to release the engagement mechanism from engagement with the driven shaft, the method comprising rotating the drive shaft from a freewheel position in one of a clockwise and a counterclockwise direction, whereby the engagement mechanism is moved into an engagement position so as to rotate the driven shaft, and returning the drive shaft to the freewheel position. The drive shaft may be rotatable in each of the clockwise and counterclockwise direction. The driven shaft may be freely rotating in one of the clockwise and the counterclockwise direction prior to the rotating of the drive shaft.